This invention relates to the making and using of biomedical electrodes.
Modern medicine employs many medical procedures where electrical signals or currents are received from or delivered to a patient""s body. The interface between medical equipment used in these procedures and the skin of the patient usually includes a biomedical electrode. Such an electrode typically includes a conductor connected electrically to the equipment and a conductive medium adhered to or otherwise in contact with the patient""s skin.
Therapeutic procedures and devices that make use of biomedical electrodes include transcutaneous electronic nerve stimulation (TENS) devices for pain management; neuromuscular stimulation (NMS) techniques for treating conditions such as scoliosis; defibrillation electrodes for dispensing electrical energy to a chest cavity to defibrillate the heart; and dispersive electrodes to receive electrical energy dispensed into an incision made during electrosurgery.
Diagnostic procedures that make use of biomedical electrodes include electrocardiograms (ECGs) for monitoring heart activity and diagnosing heart abnormalities.
Representative examples of biomedical electrodes that have been used for, or described as useful for, diagnostic purposes include U.S. Pat. Nos. 4,352,359 (Larimore); 4,524,087 (Engel); 4,539,996 (Engel); 4,554,924 (Engel); 4,848,348 (Carim); 4,848,353 (Engel); 5,012,810 (Strand et al.); 5,133,356 (Bryan et al.); 5,215,087 (Anderson et al.); and 5,296,079 (Duan et al.), the entire contents of which are hereby incorporated by reference.
For diagnostic applications, non-polarizable electrodes, and in particular silver/silver chloride electrodes, have become the current collectors of choice because of their high electrical stability. In low-cost versions, these electrodes are coated in thin sections from a conductive ink containing silver/silver chloride particles and a polymeric binder onto an insulating backing. While silver/silver chloride electrodes are reasonably resistant to corrosive attack and generally have a long shelf-life, under certain gel conditions such as a low pH in conjunction with a high water content and high chloride concentration, they can undergo accelerated corrosion and exhibit premature electrical failure.
To control corrosion in biomedical electrodes, sacrificial anodes have been interwoven in an electrode assembly and electrically connected to a current collector. While functional, such protection may not be cost-effective due to design constraints and added material costs.
Alternative for silver/silver chloride materials have also been proposed for biomedical electrodes, among them titanium hydride and certain carbon-containing materials. Such arrangements, however, are generally unduly complex, expensive and material-intensive.
There remains a need, therefore, for corrosion-resistant biomedical electrodes that are simply constructed and relatively cost-effective.
In one aspect, the present invention provides a non-polarizable biomedical electrode that is protected against corrosion by an organic corrosion retarding agent. The biomedical electrode comprises a conductor in contact with a conductive medium, wherein the conductor comprises a conductively active source of at least partially chlorided silver and wherein the electrode includes at least one organic corrosion retarding agent.
In another aspect, the invention provides a biomedical electrode comprising a conductor in contact with a conductive medium, wherein the conductor comprises a substrate having at least partially chlorided silver thereon and wherein the silver has been treated with an organic corrosion retarding agent.
In still another aspect, the invention provides methods of preparing biomedical electrodes, the methods generally comprising the steps of:
preparing a conductor having a conductive layer comprising partially chlorided silver and at least one organic corrosion retarding agent; and
applying a layer of conductive medium to the conductive layer.